Temperature compensated oscillator and control method thereof

Abstract

A temperature compensated oscillator and a control method are provided. The oscillator includes a Micro Electro Mechanical Systems (MEMS) resonator group, a heating device, and a controller. The MEMS resonator group includes a first MEMS resonator and a second MEMS resonator. The first MEMS resonator outputs a main oscillation frequency according to a control signal. The second MEMS resonator outputs an auxiliary oscillation frequency according to a temperature of the second MEMS resonator. The heating device increases a temperature of the MEMS resonator group. The controller controls the heating device according to a difference between the main oscillation frequency and the auxiliary oscillation frequency. In the control method, at first, the MEMS resonator group is provided. Thereafter, a frequency difference between the main oscillation frequency and the auxiliary oscillation frequency is calculated. Then, the temperature of the MEMS resonator group is controlled according to the frequency difference.

What is claimed is: 
     
         1 . A temperature compensated oscillator, comprising:
 a micro electro mechanical systems (MEMS) resonator group, comprising:
 a first MEMS resonator, configured to output a first periodic signal in accordance with a control signal, wherein the first periodic signal has a main oscillation frequency; and 
 a second MEMS resonator, configured to output a second periodic signal in accordance with temperature of the second MEMS resonator, wherein the second periodic signal has an auxiliary oscillation frequency; 
   a heating device, configured to increase temperature of the MEMS resonator group; and   a controller, configured to control the heating device in accordance with a difference between the main oscillation frequency and the auxiliary oscillation frequency, wherein the controller comprises:
 a counter, configured to calculate a frequency difference between the main oscillation frequency and the auxiliary oscillation frequency; and 
 a temperature control unit, configured to control the heating device in accordance with the frequency difference. 
   
     
     
         2 . The temperature compensated oscillator of  claim 1 , wherein a first slope of a first relationship curve representing a relationship between the main oscillation frequency and the temperature of the MEMS resonator group is not equal to a second slope of a second relationship curve representing a relationship between the auxiliary oscillation frequency and the temperature of the MEMS resonator group. 
     
     
         3 . The temperature compensated oscillator of  claim 1 , comprising:
 a first gain stage circuit, disposed between the first MEMS resonator and the counter to amplify the first periodic signal; and   a second gain stage circuit, disposed between the second MEMS resonator and the counter to amplify the second periodic signal.   
     
     
         4 . The temperature compensated oscillator of  claim 3 , wherein the first gain stage circuit and the first MEMS resonator forms a Pierce oscillator, and the second gain stage circuit and the second MEMS resonator forms another Pierce oscillator. 
     
     
         5 . The temperature compensated oscillator of  claim 3 , wherein the first gain stage circuit and the first MEMS resonator forms a Copitts oscillator, and the second gain stage circuit and the second MEMS resonator forms another Copitts oscillator. 
     
     
         6 . The temperature compensated oscillator of  claim 1 , comprising a digital-to-analog converter, wherein the temperature control unit controls the heating device in accordance with a first voltage control code and a second voltage control code, and the digital-to-analog converter is configured to respectively convert the first voltage control code and the second voltage control code to a first temperature control voltage and a second temperature control voltage, and the heating device provides heat energy to the MEMS resonator group in accordance with a voltage difference between the first temperature control voltage and the second temperature control voltage. 
     
     
         7 . The temperature compensated oscillator of  claim 1 , wherein the first MEMS resonator includes material having a positive temperature coefficient of frequency (TCF). 
     
     
         8 . A method for controlling a temperature compensated oscillator, comprising:
 providing a MEMS resonator group, wherein the MEMS resonator up comprises a first MEMS resonator and a second MEMS resonator;   driving the first MEMS resonator to output a first periodic signal, wherein the first periodic signal has a main oscillation frequency;   driving the second MEMS resonator to output a second periodic signal, wherein the second periodic signal has an auxiliary oscillation frequency;   calculating a frequency difference between the main oscillation frequency and the auxiliary oscillation frequency; and   performing a temperature control operation to control a heating device to adjust temperature of the MEMS resonator group.   
     
     
         9 . The method of  claim 8 , wherein the heating device adjusts the temperature of the MEMS resonator group in accordance with a first voltage control code and a second voltage control code. 
     
     
         10 . The method′ of  claim 9 , wherein the temperature control operator comprises:
 calculating a compensation temperature value of the MEMS resonator group in accordance with the frequency difference and a standard value of frequency difference; and 
 calculating the first voltage control code and the second voltage control code in accordance with the compensation temperature value.